e.g., given a LDAP_SYSCONFDIR of /etc/openldap the default config
directory is /etc/openldap/slapd.d.

Our site has two schema directories: The directory which OpenLDAP
installs with its own schema files, and a directory outside
LDAP_SYSCONFDIR with our other schema files. LDAP_SYSCONFDIR contains
the OpenLDAP version name, so we have to copy the configuration (*.conf)
from the last installation to the current one and edit it a bit.

It's not the biggest problem in the world to create symlinks between the
two, but if others have the same setup, remember that there are
filesystemes that do not support symlinks. And _copying_ schema files
from the private schema directory to the installation directory could
easily lead to mismatches - one would edit a file in one directory but
forgot to copy it to the others.

First of all, schema files are not the sort of thing that get edited
frequently. Secondly, all of the old-style config files are being phased
out. Only LDIFs should be actively maintained on a 2.3 installation. As
I posted already, you can continue to do things the old way, but it
would be advantageous to migrate to the new and stay there.